1. Field of the Invention
The invention relates to a process for preparing a composition of so-called mixed crystalline particles, especially monocrystalline nanoparticles, including at least one element from column 13 (group III) and at least one element from column 15 (group V) of the table of the periodic system of the chemical elements.
2. Description of the Related Art
The production of such mixed crystalline particles under conditions which are economical and compatible with operation on an industrial scale represents a major challenge, especially in view of their diverse applications such as, for example, in satellite TV receivers, optical fibres for communications, CD readers, barcode readers, flat and LED screens, photovoltaic cells, etc.
Despite intensive research on the subject, all the known processes (see in particular Jennifer Chia-Jen Hsieh “Synthesis, characterization and biotemplated assembly of Indium nitride and indium gallium nitride” Massachusetts Institute of Technology, 16 Jul. 2010; Micic O I et al. “Synthesis, structure, and optical properties of colloidal GaN quantum dots” Applied Physics Letters, Vol. 74, No. 4, 26 Jul. 1999 pp. 478-480; US2007/256629) require treatment at high temperature (always above 100° C.).
In addition to physical processes at high pressure and high temperature, there has been proposed a reduction reaction in solution (see especially WO2006/099386) starting from a precursor salt of an element of group III (GaCl3 in the example), a precursor formed of a mono-, di- or tri-alkyl compound of an element of group V ((C2H5)3N in the example) or a precursor formed of a chelate of an element of group III with a mono-, di- or tri-alkyl compound of an element of group V, in the presence of a reducing agent (KBH4 in the example, or a different metal hydride) in a solvent (acetonitrile or triethylamine in the example). In order to obtain crystalline nanoparticles, a temperature at least greater than 180° C. (200° C. in the example) is necessary. The synthesis can optionally be carried out in the presence of an encapsulating agent (TOPO in the example). Furthermore, subsequent steps of purification and extraction of the nanoparticles are necessary, especially in order to remove by-products such as KCl.